Overload-responsive electric switchoperating device



W. L. COWAN Nov. 9, 1965 OVERLOAD-RESPONSIVE ELECTRIC SWITCH-OPERATING DEVICE Filed April 19, 1965 Ill INVENTOR. WILLIAM L. cow/w ATTOFAIEYS' United States Patent 3,217,128 OVERLOAD-RESPONSIVE ELECTRIC SWITCH- OPERATING DEVICE William L. Cowan, St. Clair Shores, Mich., assiguor to Scientific Products Inc., Detroit, Miclr, a corporation of lVIichigau Filed Apr. 19, 1963, Ser. No. 274,076 3 Claims. (Cl. 200-153) This invention relates to electric power safety devices and, in particular, to overload-responsive electric switchoperating devices.

One object of this invention is to provide an overload responsive electric switch-operating device which will automatically break the electrical energization circuit of an electric power device, such as an electric motor, by mainly mechanical means which are positively operative to shift an electric power control switch immediately upon the development of an overload without dependence upon prior thermal-responsive devices which might fail to protect in an emergency, particularly after a long period of use.

Another object is to provide an overload-responsive electric switch-operating device of the foregoing character wherein the shutoff mechanism includes a pair of rotary members adapted to be frictionally rotated automatically upon the slowing down or halting of a power output shaft in response to the development of an overload therein while the power input element, such as a gear or pulley, continues to rotate, with the result of displacing one of the rotary members relatively tothe other rotary member and thereby operating the control switch, which is operatively engaged by the shifted rotary member.

Another object is to provide an overload-responsive electric switch-operating device as set forth in the object immediately preceding, wherein an actuating element interposed between the two rotary members is caused to push one of the rotary members away from the other rotary member upon the development of such overload and actuate the control switch.

Other objects and advantages of the invention will become apparent during the course of the following description of the accompanying drawing, wherein:

FIGURE 1 is a central vertical section through an overload-responsive electric switch-operating device, according to one form of the invention, with the power shutoff control switch shown diagrammatically, taken along the line 11 in FIGURE 2;

FIGURE 2 is a cross-section partly in top plan view, taken along the line 2--2 in FIGURE 1, showing the lower rotary member thereof; and

FIGURE 3 is a cross-section, mainly in bottom plan view taken along the line 3-3 in FIGURE 1, showing the upper rotary member thereof.

Referring to the drawing in detail, FIGURE 1 shows an overload-responsive electric switching-operating device, generally designated 10, as mounted between upper and lower frame members 12 and 14 containing upper and lower flanged sleeve bearings 16 and 18 which rotatably support a vertical rotary output shaft 20. The upper bearing 16 directly supports the output shaft 20, whereas the lower bearing 18 rotatably supports a sleeve 22 counterbored at its upper and lower ends to receive sleeve bearings 24 and 26 which in turn directly and rotatably support the lower portion of the output or driven shaft 20. Keyed or otherwise drivingly secured to the upper end of the output shaft above a spacing collar 27 is a rotary power output member 29, such as a sprocket.

The sleeve 22 is recessed at 28 to drivingly receive the inner end of a set screw 30 which is threaded through an oblique hole 32 in a rotary driving or input element 34, such as a gear, pulley, sprocket or equivalent device, a gear being shown for purposes of illustration but not limitation. The driving gear 34 is provided with a fiat clutching face 36 which is engaged by the upper correspondingly flat side of a friction disc 38, the latter being centrally bored for the passage of the shaft 20. The lower side of the disc 38 is secured as a clutch facing to the face 40 of a rotary clutch plate or driven element 42. The latter is broached or otherwise provided with a fiatsided bore 44 for drivingly receiving the corresponding flat-sided lower end portion 46 of the output shaft 20 and counterbored as at 48 for the reception of convexo-concave spring washers 50 which are urged against the bottom of the counterbore 48 by a nut 52 threaded upon the threaded portion 46 of the shaft 20. In this manner a frictionally-actuated driving effort is transmitted from the driving gear or other driving member 34 to the output shaft 20 but yieldable in the event of an overload sufficient to cause slippage between the driving member 34 and the clutch facing 38.

Mounted on the flat top surface 58 of the sleeve 22 is the correspondingly fiat bottom 60 of a cup-shaped overload-sensing member 62 which is centrally bored for the loose and rotatable passage of the shaft 20. Disposed within the cupped overload-sensing member 62 is a ball thrust bearing 64 which in turn is engaged by a washer 66 held in position by a spring snap ring 68 engaging a groove 70 in the adjacent portion of the shaft 20. In this manner, pressure is exerted between the clutch pressure plate 42, clutch facing 38 and driving member 34, by means of the adjusting nut 52 and compression spring washers 50, which may be of the so-called Belleville or Schnorr type, well known to those skilled in the mechanical arts, this pressure being resisted by the snap ring 68, washer 66 and thrust bearing 64 in such a manner as to provide a frictional drive between the upper end 58 of the sleeve 22 and the bottom 60 of the cupped overloadsensing member 62.

The upper flat face 70 of the cupped overload-sensing member 62 frictionally engages an annularly-rabbetted surface 72 on the bottom of a cupped rotary abutment member 74 containing on its upper face an annular channel 76, the bottom of which is provided with circumferentially-spaced approximately hemispherical recesses '78 (FIGURE 2). Mounted in the channel 76 of the abutment member 74 are at least two rotation-transmitting elements 80 of cross-shaped form with centers 31 and with multiple round-ended arms 82. The rotation transmitting elements 80 are spaced at approximately equal circumferential intervals around the annular channel 76, with their rounded lower ends 84 engaging two adjacent recesses 78 while their rounded upper ends 84 simultaneously engage two corresponding-adjacent approximately hemispherical recesses 86 (FIGURE 3) in the lower face 88 of a rotary electric switch operating member or disc 90 loosely and rotatably mounted on the output shaft 20 and urged downwardly by a torsion compression spring 92. The lowest convolution of the torsion spring 92 engages the disc 90 and urges it downwardly against the rotationtransmitting elements 80 whereas the upper end is held in position in any suitable way such as by the spring snap ring 94 snapped into the snap ring groove 96 in the output shaft 20. The switch shutoff disc 90 is provided with an axial hub 98 having an enlarged bore 100 loosely and relatively slidably receiving the output shaft 20. The lower portion of the torsion spring 92, which is in a state of compression, encircles the hub 98.

Spaced a short distance above the upper face 102 of the switch operating member or disc 90 is the operating end button 104 of the movable switch arm 106 of a safety electric power shutoff switch, generally designated 108. The movable arm 106 is provided with a movable con- O tact 110 which is normally engaged with a lower fixed contact 112 on a lower stationary switch arm 114, whereas it is engaged upon upward swinging of the movable switch arm 1% with an upper fixed contact 116, upon an upper stationary switch arm 118. The movable switch arm 166 is pivoted to an output terminal 120, whereas the lower and upper stationary switch arms 114 and 118 are provided with connection terminals 122 and 124 .respectively.

In the operation of the invention, let it be assumed that the parts are in the positions shown in FIGURE 1, and that power from an outside source such as an electric motor or hydraulic motor drives the driving member 34 so as to drive the clutch plate 42 frictionally through the clutch facing 33. The consequent rotation of the power output shaft 20 and rotary output member 29 drives the external machinery subject to overloads such as, for example, a conveyor, overhead door operating mechanism or the like. If an overload develops in the machinery connected to the power output member 29 so as to slow down or halt the power output shaft 20, slippage occurs between the rotary power input member 34 and the clutch facing 38, while the sleeve 22 continues to be driven through its driving connection by the set screw 3!) (FIGURE 1). The consequent upward thrust applied by the spring washers 5th to the clutch plate 42 and thence through the clutch facing 33 to the lower end of the sleeve 22 causes the latter to rotate the cup-shaped overload sensing member 62 through the frictional engagement of the surfaces 58 and 60. This in turn causes rotation of the rotary abutment member '74- through the frictional engagement of the surfaces 70 and 72.

The rotation of the rotary abutment member 74 by the engagement of its recesses 73 with the rounded lower ends 84 of the cross-shaped rotation-transmitting mem- 7C1S tit) causes the latter to walk in an annular path while rotating around their centers 81 as axes. The consequent moving of. the arms 32 from their normal positions oblique to the axis of the shaft 20 (FIGURE 1) to vertical positions approximately parallel to the axis of the shaft 2t? pushes the switch operating member or disc 99 upward away from the abutment member 74 against the thrust of the torsion spring 92 while rotating the latter through the engagement of the rounded upper ends 84 of the rotation-transmitting members St). The upward motion of the upper surface 102 of the switch operating member or disc 90 pushes the button 10- of the movable switch arm 1% upward, disengaging its movable contact 110 from the lower stationary switch contact 112 and engaging it with the upper stationary switch contact 1.16. This action of the control switch 198 is communicated to an external control circuit connected to the terminals 122 and of the stationary switch arms 114 and 11S and to the terminal 126 of the movable switch arm 106, operating a relay or relays or other conventional electric apparatus (not shown) which in turn tie-energizes and halts the motor or other prime mover supplying power to the rotary driving element 34.

What I claim is:

1. An overload-responsive electric switch-operating device, comprising a supporting structure,

a rotary power output shaft rotatably mounted in said supporting structure,

a rotary driven element drivingly connected to said shaft,

a rotary driving element rotatably mounted adjacent said driven element,

a rotary load-sensing abutment member abutting said rotary driving element in frictional driven engagement therewith,

means yieldingly urging said driving element into yielding driving engagement with said driven element and said loadsensing member into yielding driven engagement with said driving element,

a switch-operating member spaced axially away from said load-sensing abutment member in relativelyrotatable axially-slidable relationship therewith,

a plurality of circumterentially-spaced multiple-armed rotation-transmitting elements spaced radially away from the axis of said shaft disposed between said members with their arms normally disposed oblique to said axis and responsive to rotation of said loadsensing abutment member relatively to said switchoperating member for rotating said arms toward parallelism with said axis and thereby moving said switch-operating member axially away from said load-sensing abutment member,

and an electric switch. having an operating part positioned in the path of said switch-operating member for shifting thereby in response to axial motion thereof relatively to said load-sensing abutment member.

2. An overload-responsive electric switch-operating device, according to claim 1, wherein a thrust bearing is mounted on said shaft adjacent said load-sensing abutment member in axial shift-preventing relationship with said shaft.

3. An overload-responsive electric switch operating device, according to claim 2, wherein said members have rounded recesses in the adjacent faces thereof and wherein the arms of said multi-armed elements have rounded opposite ends rockably engageable with said rounded recesses.

References Cited. by the Examiner UNITED STATES PATENTS 3,038,576 6/62 Simpson l92150 BERNARD A. GILHEANY, Primary Examiner. 

1. AN OVERLOAD-RESPONSIVE ELECTRIC SWITCH-OPERATING DEVICE, COMPRISING A SUPPORTING STRUCTURE, A ROTARY POWER OUTPUT SHAFT ROTATABLY MOUNTED IN SAID SUPPORTING STRUCTURE, A ROTARY DRIVEN ELEMENT DRIVINGLY CONNECTED TO SAID SHAFT, A ROTARY DRIVING ELEMENT ROTATABLY MOUNTED ADJACENT SAID DRIVEN ELEMENT, A ROTARY LOAD-SENSING ABUTMENT MEMBER ABUTTING SAID ROTARY DRIVING ELEMENT IN FRICTIONAL DRIVEN ENGAGEMENT THEREWITH, MEANS YIELDINGLY URGING SAID DRIVING ELEMENT INTO YIELDING DRIVING ENGAGEMENT WITH SAID DRIVEN ELEMENT AND SAID LAOD-SENSING MEMBER INTO YIELDING DRIVEN ENGAGEMENT WITH SAID DRIVING ELEMENT, A SWITCH-OPERATING MEMBER SPACED AXIALLY AWAY FROM SAID LOAD-SENSING ABUTMENT MEMBER IN RELATIVELYROTATABLE AXIALLY-SLIDABLE RELATIONSHIP THEREWITH, A PLURALITY OF CIRCUMFERENTIALLY-SPACED MULTIPLE-ARMED ROTATION-TRANSMITTING ELEMENTS SPACED RADIALLY AWAY FROM THE AXIS OF SAID SHAFT DISPOSED BETWEEN SAID MEMBERS WITH THEIR ARMS NORMALLY DISPOSED OBLIQUE TO SAID AXIS AND RESPONSIVE TO ROTATION OF SAID LOADSENSING ABUTMENT MEMBER RELATIVELY TO SAID TOWARD OPERATING MEMBER FOR ROTATING SAID ARMS TOWARD PAALLELISM WITH SAID AXIS AND THEREBY MOVING SAID SWITCH-OPERATING MEMBER AXIALLY AWAY FROM SAID LOAD-SENSING ABUTMENT MEMBER, AND AN ELECTRICAL SWITCH HAVING AN OPERATING PART POSITIONED IN THE PATH OF SAID SWITCH-OPERATING MEMBER FOR SHIFTING THEREBY IN RESPONSE TO AXIAL MOTION THEREOF RELATIVELY TO SAID LOAD-SENSING ABUTMENT MEMBER. 